1. Field of the Invention
The present invention relates to a fixing device and a fixing method in which an image is fixed onto a recording material while supplying power to a heating part of a fixing roller from a storage unit, and to an image forming apparatus including the fixing device.
2. Description of the Related Art
A fixing device that fixes a toner image formed on a recording material, such as a recording sheet, via a heating part having a main heating element and an auxiliary heating element has been widely used. In this fixing device, the main heating element is powered by a main power supply unit, and the auxiliary heating element is powered by an auxiliary power supply unit including a capacitor. The auxiliary power supply unit is charged by an external power source through the main power supply unit when the main power supply unit does not supply power to the main heating element, and the auxiliary power supply unit is not charged by the external power source through the main power supply unit when the main power supply unit supplies power to the main heating element.
Published Japanese patent application No. 2003-257590 describes the above fixing device. The fixing device enhances the power-saving effect with a simple configuration. Further, an installation space is reduced by reducing the size of the auxiliary power supply unit.
In a fixing device using a main power supply unit and an auxiliary power supply unit including a capacitor that supply power to a heating part, it is desirable to charge the auxiliary power supply unit acting as a storage unit by effective use of electric power of an external power source; and to enhance the quality of an image fixed on a recording material even if the fixing device is in a low temperature condition.